The invention relates generally to material processing and, more particularly, the invention pertains to a method for producing preselected patterns of biochemical materials on substrate surfaces, and the patterned substrates produced thereby.
A great deal of consideration has been given in recent years to the chemical and biological uses of micro and nanoelectromechanical systems (MEMS and NEMS). For example, see R. F. Taylor, in Handbook of Chemical and Biological Sensors, R. F. Taylor et al., eds., Institute of Physics Publishing, Bristol, UK (1996) at page 553; R. J. Foster, in Principles of Chemical and Biological Sensors, D. Diamond, ed., John Wiley and Sons, Inc. N.Y. (1998) at p. 235; A. F. Collings et al., Rep. Prog. Phys., 60, 1397 (1997); B. Ilic et al., Appl. Phys. Lett., 77, 450 (2000); D. W. Carr et al., J. Vac. Sci. Technol. B, 16, 3821 (1998) and S. Turner et al., op. cit., 15, 2848 (1997). Physical sensors, in general, are based on a mature technology and have many commercial manifestations, however, biological sensor technology is still emerging and few commercial products are found in the clinical setting. For example, see I. Amato, Technology Rev., 74 (1999); L. J. Kricka, Nature Biotech., 16, 513 (1998). One of the crucial features in the fabrication of effective biosensors is the development of immobilization technologies for stabilizing biomolecules and tethering them to surfaces in selected device areas. The ability to generate mesoscopic (0.1 xcexcm-10 xcexcm) area patterns of biological materials offers new applications for these engineered biomolecular surfaces in the field of cell culturing, tissue engineering, biosensor technology, drug discovery, and nanotechnology. For example, see R. Singhui et al., Science, 204, 696 (1994); E. Delmarche et al., Science, 276, 779 (1997); C. S. Chen et al., op. cit., at page 1425; C. D. James et al., Langmuir, 4, 741 (1998); S. Takayama et al., PNAS USA, 96, 5545 (1999); P. M. St. John et al., Anal. Chem., 70, 1108 (1998); M. J. Feldstein, J. Biomed. Microdevices, 1, 139 (1999); and R. Kapur et al., op cit., 2, 99 (1999).
Microcontact printing (xcexcCP) can be used as a parallel lithography technique for localized geometric confinement of self-assembled monolayers (SAM), as well as various chemically sensitive polymers and biological materials. For example, see, H. A. Biebuyck et al., IBM J. Res. Devel., 41, 159 (1997); N. B. Larsen et al., JACS, 119, 3017 (1997); I. Yan et al., JACS, 120, 6179 (1998); B. A. Grzybowski et al., Anal. Chem., 70, 4645 (1998); P. Yang et al., Science, 282, 2244 (1998) and E. Delmarche et al., J. Phys. Chem. B, 102, 3324 (1998). The method is based on utilizing a xe2x80x9cstampxe2x80x9d made from poly(dimethylsiloxane) (PDMS) elastomer to transfer biological material so as to form a layer of patterned material on the surface of a substrate by a covalent chemical reaction. The patterns serve as an etch mask to subsequent chemical etching of the underlying layer. Submicrometer features over areas greater than 1 cm2 have been etched in gold using microcontact printing. There are, however, several drawbacks with xcexcCP, such as pairing and sagging of the stamp, evolving from the elastomeric properties of PDMS (Y. Xia et al., Angew. Chem. Int. Ed., 37, 550 (1998)). Furthermore, PDMS tends to shrink upon curing and swell when in contact with nonpolar solvents.
Thus, a need exists in the art for new approaches to patterning biological materials on solid surfaces that allow for proper placement and consistent and repeatable patterning, under processing conditions that do not limit or destroy the biological materials being patterned on the surface.
The present invention provides a method of patterning a wide variety of inorganic and organic materials, and is particularly well-adapted to pattern biological materials on a substrate comprising coating a substrate surface with a releasable polymer coating, creating one or more openings through the polymer coating to expose a portion of the substrate surface in a predefined pattern, coating at least a portion of the substrate surface that is exposed through the polymer coating with at least one preselected material, such as a metal or a biological material, and optionally removing said polymer coating so that the material is retained on said substrate surface is said predefined pattern.
Thus, the present invention provides a method that accomplishes the proper placement and the consistently repeatable patterning of materials on target surfaces. The patterning is carried out under processing conditions that do not inhibit or destroy the material that is patterned on the surface. For example, the present invention also provides an efficient and economical method of producing micrometer sized patterns of cells or other biomaterials over large areas.
A preferred embodiment of the present method can be referred to as a xe2x80x9cdry lift-offxe2x80x9d method that allows patterning of chemically sensitive materials, such as biological materials, on a variety of surfaces. Using a combination of projection lithography and reactive ion etching, a surface coated with an inert flexible polymer is patterned and subsequently coated with a layer of one or more preselected materials. The polymer film is peeled from the substrate surface and the desired pattern of residual material is formed. The present method is exemplified by the production of silicon wafers patterned with antibodies, poly-L-lysine and aminopropyltriethoxysilane (APTS) self-assembled monolayers. These surfaces were respectively used to pattern Escherichia coli serotype O157:H7 bacteria cells, rat basophilic leukemia (RBL) cells and 20 nm diameter aldehyde-sulfate coated fluorescent polystyrene beads. Typical patterns consisted of arrays of 5 mm long parallel lines of bacteria confined to stripes with widths varying from 2 xcexcm to 20 xcexcm. Such pattern can be made over large areas, e.g., areas up to 3 cm2 or greater.
The present method permits the construction of geometrically well-defined regions of materials such as biochemicals, tissues and cells. The present method offers several advantages over traditional cell patterning methods. The present microfabrication techniques pattern a chemically inert polymer with a high degree of dimensional control in order to shape and confine the layer of preselected material. Using a polymer that is both chemically inert and thermally stable over a wide range of temperatures, permits the selective immobilization of a wide variety of materials, such as biologicals, and any other chemically sensitive materials.
The method provides an efficient and economically practical technique to reproduce micrometer sized patterns over areas spanning many cm2. One of the desirable and significant applications of this technology is to develop new types of rapid detection, fully integrated, high sensitivity, biological sensors and systems for screening of pharmaceuticals, detection of toxins, microanalysis of proteins, and DNA sequencing. For instance, the present method can readily integrate bioMEMS and bioNEMS devices with the complementary metal oxide semiconductor (CMOS) post-processing technology, thus enabling highly flexible, reproducible, high yield, low cost, batch fabrication of smart biological sensors. For example, see, Y. T. C. Yeh et al., J. Vac. Sci. Technol. A, 2, 604 (1983); D. T. Price et al., Thin Solid Films, 309-309, 523 (1997) and S. Rogojevic et al., J. Vac. Sci. Technol. A, 17, 266 (1999).
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.